*ed hobbles in on his cane, sits in the rocking chair and begins to recollect about the women in his life...remembers that isn't the subject and ....*
like Phil said, this isn't going to be a therapist type answer. more the shared experience of a guy who had a horrible time with women till he was about 17 and then read the book "how to pick up women" (for real
).
first, phil's advice is pretty good. except i would never give a girl my number and expect her to call. i would get her number and call her in a day or 2. If she gives you the number she is definitly interested in you for some reason. it still could be as friends though.
one good indication i found is that a girl who is flirting will tend to touch you physically. this can be a bit confusing with younger girls who still haven't figured out the effect/affect physical contact has on males, but for most girls this is true. another good indication is her eyes. if she is flirting she will either tend to stare at you or to consciously avoid eye contact. a friend will casually make eye contact and then shift away and then make eye contact and then look away, etc. a girl with an interest in you will either want you to know or will look quite awkward trying to keep you from knowing.
this may sound hard to believe, but girls have all the same fears and confusions about guys. they are also afraid of being rejected and hurt. afraid of being emabarassed or of things not being what they seem with a guy. so unless this is the most popular girl in school, she likely
could be interested if she approaches you at all for any reason other than to get you to do her homework for her. the real thing is to be brave enough to be a bit flirtatious yourself. you need to let a girl you are interested in know how you feel. do it nicely and she will feel good about it even if she doesn't feel the same. and believe me the relief of knowing where you stand is better than being in limbo and being self conscious about your every move.
oh, and last thing - flirtation normally uses feeling words and subtle body language. also it contains compliments. if a girl tells you that you are cute or you have nice legs or she "likes" something about you that seems wierd to you, then that is flirting.
warning - teenage girls (well, lots of females of all ages really) sometimes like to flirt for their own gratification. they are interested in getting attention and making themselves feel better. they may have no other interest in the male they are talking to beyond that. flirting doesn't always mean something else is in the possible future. so again, being clear on how you feel is the best solution. the more you do this, the better feel you will get for what is really going on with women.
and trip - don't get too hung up worrying about high school girls. once you get to college, women are slightly more mature and easier to deal with. high school is a great time to make lots of mistakes. chances are you'll never see 90% of these girls again after HS, except for reunions. at which point they will all be interested if you have learned to apply all you learned from them.
(or you'll be happily settled with a woman who doesn't treat you like they did and can just laugh at them)
oh, and never discount the advantages of friendship. being friends with a girl will get you access to their friends. plus many great relationships start as friends and then develop into something else.